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Post subject: Tube Knowledge
Posted: Fri Jul 19, 2013 10:21 pm
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I was talking to a buddy of mine about tubes because his burnt, so I was looking at tubes. What is the difference between an 12AX7, 12AU7, and 12AT7? I know a little bit about tubes, but not like some, guitars are more my thing. I know some have a lower gain, quieter, smoother tone. And I know what position the tubes are in it is a certain stage in the preamp so different tubes at different positions get different tones. Anyone can clarify this for me, just looking for general tube knowledge


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Post subject: Re: Tube Knowledge
Posted: Fri Jul 19, 2013 11:46 pm
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It is about gain factor of each tube, the 12AX7 having the highest gain factor. As you've noted, lower gain tubes typically give a cleaner sound. Here is a cool chart that shows the gain factor of various preamp tubes.

http://www.thetubestore.com/Resources/Guitar-Amp-Info/Gain-Factor

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Post subject: Re: Tube Knowledge
Posted: Fri Jul 19, 2013 11:52 pm
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Thanks goodness for the Net. We oldsters had to learn all this through reading dog-earred books, watching master techs, and school of hard knocks.

Tip of the iceberg....


One of the better initial sources:

http://www.aikenamps.com/TI_Aiken_int.htm


More Advanced:

http://www.aikenamps.com/TI_Aiken_adv.htm


More design considerations:

http://www.valvewizard.co.uk/


And even more:

http://www.tone-lizard.com/Table_Of_Contents.htm


One of MANY DIY sites:

http://www.ax84.com/


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Post subject: Re: Tube Knowledge
Posted: Sat Jul 20, 2013 2:52 am
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Or, if you're really old, you learned it in college. :shock: :lol:

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Post subject: Re: Tube Knowledge
Posted: Wed Jul 24, 2013 8:37 pm
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shimmilou wrote:
Or, if you're really old, you learned it in college. :shock: :lol:


Or military tech school......

Arjay

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Post subject: Re: Tube Knowledge
Posted: Wed Jul 24, 2013 11:05 pm
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OR if you are dead you may have pioneered the valve. :lol: :lol: :lol:

I love modern technology, but often I really wish I lived way before my time.

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Post subject: Re: Tube Knowledge
Posted: Fri Jul 26, 2013 4:06 am
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AaronK wrote:
OR if you are dead you may have pioneered the valve. :lol: :lol: :lol:

I love modern technology, but often I really wish I lived way before my time.


I agree, hearing my parents talk about the 50's and 60's make me wish I was alive back then, and for music gear, I mean there is a reason people are after Vintage Strats, Les Pauls, Fender Amps, Marshalls, etc


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Post subject: Re: Tube Knowledge
Posted: Sat Jul 27, 2013 1:27 pm
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A must-have for anyone interested in vacuum tubes and tube-amp theory is the RCA Receiving Tube Manual, edition RC26 or newer. This detailed volume covers the nuts and bolts of the most popular tubes and includes prolific circuit designs that are used by many amp manufacturers.

The books mentioned by BMW2002ti previously are also great reference tools.

Arjay

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Post subject: Re: Tube Knowledge
Posted: Sat Jul 27, 2013 3:21 pm
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For PDF versions of most RCA Receiving Tube manuals, and many other manufacturers tube manuals and info.

http://www.tubebooks.org/tube_data.htm

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Post subject: Re: Tube Knowledge
Posted: Mon Jul 29, 2013 6:44 am
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The right tube can make most amps sing..Got to like finding that pre amp tube that makes for smooth tone..Top stuff..


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Post subject: Re: Tube Knowledge
Posted: Mon Sep 02, 2013 5:52 pm
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bigcribber42 wrote:
I was talking to a buddy of mine about tubes because his burnt, so I was looking at tubes. What is the difference between an 12AX7, 12AU7, and 12AT7? I know a little bit about tubes, but not like some, guitars are more my thing. I know some have a lower gain, quieter, smoother tone. And I know what position the tubes are in it is a certain stage in the preamp so different tubes at different positions get different tones. Anyone can clarify this for me, just looking for general tube knowledge


12AX7=100% gain
12AU7=19% gain
12AT7=60% again

This of course is general understanding.

The gain factor of a tube simply measures how much it amplifies the input signal.


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Post subject: Re: Tube Knowledge
Posted: Mon Sep 02, 2013 6:43 pm
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1969spacecowboy wrote:
bigcribber42 wrote:
I was talking to a buddy of mine about tubes because his burnt, so I was looking at tubes. What is the difference between an 12AX7, 12AU7, and 12AT7? I know a little bit about tubes, but not like some, guitars are more my thing. I know some have a lower gain, quieter, smoother tone. And I know what position the tubes are in it is a certain stage in the preamp so different tubes at different positions get different tones. Anyone can clarify this for me, just looking for general tube knowledge


12AX7=100% gain
12AU7=19% gain
12AT7=60% again

This of course is general understanding.

The gain factor of a tube simply measures how much it amplifies the input signal.


Gain factor is unitless. It is useful in comparing one tube to another, but the actual in-circuit gain is what counts. A 12AX7 used in a typical preamp stage can have a gain of around 60. That same tube used in a cathode follower will exhibit unity gain (actually, slightly less).

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Last edited by bluesky636 on Mon Sep 02, 2013 8:37 pm, edited 1 time in total.

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Post subject: Re: Tube Knowledge
Posted: Mon Sep 02, 2013 8:14 pm
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1969spacecowboy wrote:
bigcribber42 wrote:
I was talking to a buddy of mine about tubes because his burnt, so I was looking at tubes. What is the difference between an 12AX7, 12AU7, and 12AT7? I know a little bit about tubes, but not like some, guitars are more my thing. I know some have a lower gain, quieter, smoother tone. And I know what position the tubes are in it is a certain stage in the preamp so different tubes at different positions get different tones. Anyone can clarify this for me, just looking for general tube knowledge


12AX7=100% gain
12AU7=19% gain
12AT7=60% again

This of course is general understanding.

The gain factor of a tube simply measures how much it amplifies the input signal.


Yeah, really mu value is only the tube independent of circuit bias parameters & feedback. Since most (like 99%) of gain stage circuits are single-ended, Class "A" there is a certain about of self-leveling between the various tube types. Plus, varying feedback constraints on each section. Both which affects the gain as much as the mu of the tube, itself.


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Post subject: Re: Tube Knowledge
Posted: Tue Sep 03, 2013 7:04 am
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bluesky636 wrote:
1969spacecowboy wrote:
bigcribber42 wrote:
I was talking to a buddy of mine about tubes because his burnt, so I was looking at tubes. What is the difference between an 12AX7, 12AU7, and 12AT7? I know a little bit about tubes, but not like some, guitars are more my thing. I know some have a lower gain, quieter, smoother tone. And I know what position the tubes are in it is a certain stage in the preamp so different tubes at different positions get different tones. Anyone can clarify this for me, just looking for general tube knowledge


12AX7=100% gain
12AU7=19% gain
12AT7=60% again

This of course is general understanding.

The gain factor of a tube simply measures how much it amplifies the input signal.


Gain factor is unitless. It is useful in comparing one tube to another, but the actual in-circuit gain is what counts. A 12AX7 used in a typical preamp stage can have a gain of around 60. That same tube used in a cathode follower will exhibit unity gain (actually, slightly less).


Sure! The question was general knowledge.... As far as 12AX7's, I've experienced various gain rates from 40% to 100%. Typically 12AX7's are the highest gain preamp tube. I've found that different company's design there 12AX7's differently, there for, one 12AX7 will function and sound different then another. And of course you could find several that function and sound the same. My experiences have taught me not all 12AX7's are created equally. I'm more of a power tube snob, but do take preamp tubes serious for they effect the power tube sound. I prefer power tube break up vs. pre amp break up. In conclusion, theory vs. reality always leaves the discussion with so many unanswered ????????'s! So, for me I'll find and dial in my own tube recipes while making great music.


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Post subject: Re: Tube Knowledge
Posted: Tue Sep 03, 2013 3:32 pm
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1969spacecowboy wrote:
Sure! The question was general knowledge.... As far as 12AX7's, I've experienced various gain rates from 40% to 100%. Typically 12AX7's are the highest gain preamp tube. I've found that different company's design there 12AX7's differently, there for, one 12AX7 will function and sound different then another. And of course you could find several that function and sound the same. My experiences have taught me not all 12AX7's are created equally. I'm more of a power tube snob, but do take preamp tubes serious for they effect the power tube sound. I prefer power tube break up vs. pre amp break up. In conclusion, theory vs. reality always leaves the discussion with so many unanswered ????????'s! So, for me I'll find and dial in my own tube recipes while making great music.


Again, "gain factor" is unit-less. There is no percentage of anything related to it.

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